Since laminated glass generates only a small amount of scattering glass fragments even when subjected to external impact and broken, laminated glass is excellent in safety. As such, the laminated glass is widely used for automobiles, railway vehicles, aircraft, ships, buildings and the like. The laminated glass is produced by sandwiching an interlayer film for laminated glass between a pair of glass plates.
Moreover, in general, since the adhesive force between an interlayer film and a glass plate is too high, laminated glass fails to absorb the impact at a collision when a human body or the like collides with the laminated glass. As such, in order to weaken the adhesive force between an interlayer film and a glass plate, an alkali metal salt, an alkaline earth metal salt, and the like are used.
As an example of the interlayer film for laminated glass prepared with an alkali metal salt or an alkaline earth metal salt, the following Patent Document 1 discloses a sound insulating layer including 100 parts by weight of a polyvinyl acetal resin with an acetalization degree of 60 to 85% by mole, 0.001 to 1.0 part by weight of at least one kind of metal salt among an alkali metal salt and an alkaline earth metal salt, and a plasticizer in an amount greater than 30 parts by weight.